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Infectious Agents 2 > Flaviviridae > Flashcards

Flaviviridae Flashcards

1
Q

Faviviridae virion properties

A
  • spherical
  • 40-60 nm diameter
  • icosahedral symmetry
  • lipid envelope
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2
Q

What is the genome type of flaviviridae?

A

Single stranded, positive sense RNA

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3
Q

What gives the virus high susceptibility in the environment?

A

Envelope

- naked viruses are more hardy in the environment

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4
Q

Positive sense RNA

A

Single strand RNA which encodes mRNA and protein

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5
Q

What are the 3 genera of flaviviridae?

A
  • pestivirus (bovine viral diarrhea virus)
  • flavivirus (yellow fever virus)
  • hepacivirus (hepatitis C virus)
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6
Q

What are 4 species of pestivirus with animal health significance?

A
  • bovine viral diarrhea virus 1
  • bovine viral diarrhea virus 2
  • classic swine fever virus
  • border disease virus
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7
Q

Bovine viral diarrhea virus has ______ distribution

A

Worldwide

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8
Q

What are the 2 biotypes of viruses?

A
  • cytopathic

- noncytopathic

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9
Q

Which biotypes are virulent in cattle?

A

Both biotypes

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10
Q

Only _______ strains induce persistent infection

A

Non-cytopathic

- non-cytopathic can mutate to cytopathic

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11
Q

What clinical disease results from bovine viral diarrhea virus?

A

Mucosal

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12
Q

Why are cytopathic biotypes not persistent?

A

They destroy the cell (and their environment) upon infectivity

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13
Q

Transmission and persistence strategies of BVD

A
  • induction of persistently infected (PI) hosts that shed and transmit BVDV efficiently
  • suppression of host’s immune system
  • transmission by various direct and indirect routes
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14
Q

BVDV transmission

A
  • direct contact and aerosols
  • blood and secretions
  • meat products
  • mechanic vectors
  • in utero infection!
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15
Q

What is the main determinant of fetal response?

A

TIming of infection!

  • embryonic death: 0-50 days after conception
  • fetal abortion/mummification: 50-100 days
  • congenital defects: 100-150 days
  • normal: 150-200 days
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16
Q

Immunocompetent

A

150-200 days after conception

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17
Q

Tolerance/persistent infection

A

Occurs when infection in utero between 80-125 days of pregnancy

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18
Q

Immune tolerance

A

Immune system is not responding because infection is too early for the immune system to recognize the foreign antigen

  • aka: state of unresponsiveness for an antigen
  • lymphocytes will not respond to an antigen if they meet that antigen early in fetal life
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19
Q

BVDV infection in susceptible immunocompetent nonpregnant cattle causes:

A
  • subclinical infection
  • bovine viral diarrhea
  • infection in neonatal calves
  • venereal infections
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20
Q

Subclinical infections causes _____ infections in adult cattle

A

70-90%

  • mild fever and leukopenia
  • development of neutralizing antibodies
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21
Q

Bovine viral diarrhea is produced by ______

A

Both biotypes

  • infect cattle 6 months - 2 years old
  • depression, ocular discharge, oral erosions, ulcerations
  • diarrhea with high morbidity and low to moderate mortality
  • lesions in coronary band and interdigital cleft
  • decrease in milk production
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22
Q

Infection in neonatal calves

A

Rarely seen in calves younger than 6 months

- severe enteritis, sometimes fatal

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23
Q

Venereal infections

A

Semen in infected bulls contains virus (transient)

- semen quality may decrease (motility and morphologic abnormalities)

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24
Q

Seronegative cows inseminated with infective semen

A

Fail to conceive until they develop an immune response

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25
Q

Mucosal disease occurs with:

A

2 biotypes of BVDV present

  • persistent infection with non-cytopathogenic virus
  • clinical signs similar to BVD but more severe
  • fever anorexia, profuse watery diarrhea, nasal discharge, erosive or ulcerative stomatitis, dehydration emaciation and death
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26
Q

Mucosal disease superinfection occurs with:

A

Cytopathogenic virus

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27
Q

Lesions

A

Acute BVD: erosive/ulcerative lesions in mouth, esophagus, forestomachs, abomasum and intestine

  • discoloration of mucosal folds (hyperemia and hemorrhage)
  • necrosis of lymphoid tissue (Peyer patches)
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28
Q

In utero infection may induce _________

A

Hypoplasia cerebellar

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29
Q

What are the rule outs for BVDV?

A
  • rinderpest
  • foot and mouth disease
  • vesicular stomatitis
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30
Q

Laboratory testing

A
  • viral isolation
  • viral antigen detection
  • RT-PCR
  • ELISA
  • ear notches
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31
Q

What laboratory test detects most persistently infected animals?

A

RT-PCR off an ear notch

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32
Q

Classic swine fever transmission

A

Main route of infection is oronasal by direct or indirect contact with infected pigs
- indirect via contaminated feed

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33
Q

Classic swine fever severity depends on:

A
  • age of the animal

- virulence of the virus

34
Q

Classic swine fever signs

A
  • acute infection: fever, depression, anorexia, conjunctivitis
  • neurological signs: staggering gait paresis, lethargic, circling, tremors, convulsions
35
Q

What are the 3 forms of classic swine fever?

A
  • peracute: kills young swine with no clinical signs
  • subacute
  • chronic: always fatal
36
Q

____ and ______ forms by strains of moderate virulence

A

Subacute and chronic

37
Q

Classic swine fever is a ______ virus that can replicate in any cell type

A

Pantropic

38
Q

Typical skin hemorrhages of classic swine fever

A

Ears, tail, abdomen and the inner side of the limbs

- appear from second or third weeks after infection until death

39
Q

Classic swine fever pathogenesis

A

Most common route by ingestion

  • replication leads to hemorrhages and leucopenia
  • disseminated intravascular coagulation, thrombosis
40
Q

Primary viral replication occurs in ______

A

Tonsils

  • goes systemically from here
  • collect a tonsil specimen to detect and diagnose CSF
41
Q

Secondary replication occurs in _______

A

Endothelial cells, lymphoid organs, bone marrow

42
Q

CSF virus causes severe leukopenia and ________

A

Immunosuppression

  • dysfunction of immune system
  • antibodies may be temporarily detected in serum, but they are not able to eliminate the virus from the host
43
Q

Lesions in the 3 forms of CSF

A
  • peracute: may be no gross changes
  • acute: generalized submucosal and subserosal petechial hemorrhages, congestion and infarction in spleen, liver, bone marrow, lungs
  • subacute + chronic: necrotic ulceration of mucosa and LI
  • chronic: exhaustion of lymphoid system, atrophy of thymus and germinal center
44
Q

________ is also a lesion of CSF

A

Non suppurative encephalitis

45
Q

Prenatal infections

A

Infection in early pregnancy may result in abortions and stillbirths, mummification and malformations

  • infections between 50-70 days of pregnancy can lead to birth of persistently viremic piglets
  • piglets shed large amounts of virus!!
46
Q

Rule outs of CSF

A
  • African swine fever
  • erysipelas
  • porcine reproductive and respiratory syndrome
  • post weaning multisystemic wasting syndrome
  • salmonella
  • pasteurella
47
Q

Recommended actions if CSF is suspected

A

Report immediately upon diagnosis or suspicion!!

48
Q

CSF samples for lab testing

A

Should be sent under secure conditions and to authorized labs to prevent spread of disease

  • blood or tissue samples from acute cases for virus isolation, antigen detection or nucleic acid detection
  • tonsils, maxillary, submandibular and mesenteric lymph nodes, spleen, kidneys, distal part of ileum
49
Q

Genus Flavivirus

A

Some viruses are arthropod-borne zoonotic pathogens

  • mosquito-borne encephalitides complex
  • tick borne virus complex
50
Q

Arbovirus

A

Viruses transmitted to vertebrate hosts by blood sucking arthropod vectors

51
Q

Flaviviruses with animal and human significance

A
  • West Nile virus
  • japanese encephalitis virus
  • louping ill virus
  • zika virus
52
Q

West Nile Virus is a member of the ______

A

Japanese encephalitis virus group

53
Q

WNV is serologically related to ______

A

St Louis encephalitis and Japanese encephalitis virus

54
Q

WNV

A

Endemic in Africa, Asia Southern Europe and North America

- transmission of virus among wild birds by infected mosquitoes

55
Q

What are important reservoirs for WNV?

A

Passerines

- jay, finches, grackles, sparrows, crows

56
Q

Principal mosquito vectors in the USA

A
  • Culex pipiens

- Culex restvans

57
Q

WNV has been isolated from over ______

A

300 species of birds

58
Q

What are the 2 groups of WNV birds?

A
  • asymptomatic: carriers
  • susceptible: crows, jays, magpies, house finches
  • –> develop neurological disease
59
Q

WNV correlates with decline of ________

A

North American bird population

60
Q

Since 1999, US has suffered a decrease of _______

A

Crow population

61
Q

WNV avian infection

A

Range from subclinical to fatal with variability among species
- neurological signs common

62
Q

WNV lesions

A
  • necrosis and enlargement of spleen and liver
  • myocardial degeneration
  • pancreatitis
63
Q

WNV disease has been reported in _____ and _____

A

Ducks and geese (poultry)

64
Q

_____, ______, and ______ are incompetent reservoirs

A

Psittaciformes, galliformes, columbiformes

65
Q

What is an important factor in disease transmission of WNV?

A

Viremia

- minimal possibility of transmitting virus from bird to mosquito unless high viremia is present

66
Q

In WNV, the mosquito becomes a ______

A

Biological vector, because it is also infected

67
Q

Mammals are considered to be _______ carriers for WNV

A

Dead-end

- viremia and viral load in blood are not sufficient to transmit WNV back to the mosquito, ending the transmission cycle

68
Q

What other animal species have been reported to show signs of WNV infection?

A

Horses

- also: goats, sheep, dog, wolf, alpaca, alligator, squirrels, crocodile, llama, cattle, seal, cat

69
Q

Mammal infection with WNV

A

Most mammals are do not play a role in enzootic transmission

  • horses: depression, abnormal gait, ataxia, muscle tremors, recumbency
  • dogs and cats: no illness!
  • humans: neuroinvasive or non-neuroinvasive form (similar to flu)
70
Q

West Nile Virus vaccine is available for ______

A

Horses

71
Q

Rule outs for WNV in horses

A
  • eastern equine encephalitis
  • venezuelan equine encephalitis
  • St. Louis equine encephalitis
  • equine herpesvirus
  • equine protozoal myeloencephalitis
72
Q

WNV diagnosis

A
  • RT-PCR

- IgM capure ELISA (acute infection)

73
Q

Japanese encephalitis

A

Infects swine, horses, dogs, chickens, ducks, reptile, humans

  • important disease for travelers
  • fewer than 1 case/year in US citizens traveling to Asia
74
Q

Japanese encephalitis symptoms

A
  • horses: encephalitis
  • swine: subclinical with abortions stillbirth, and aspermia
  • humans: leading cause of encephalitis in Asia, diarrhea, headache, myalgia, paralysis, seizures, vomiting
75
Q

Japanese encephalitis vector

A

Culex tritaeniorhynchus

76
Q

Louping ill virus

A

Important in sheep

  • seen in Europe
  • neurological signs, hopping (louping) gait, nonsuppurative meningitis and encephalomyelitis
77
Q

Louping ill virus vector

A

Tick borne

  • Ixodes ricinus
  • Rhipicephalus appendiculatus
  • humans infected via tick bites or by contact with the virus in tissues or lab cultures
78
Q

Flavivirus in humans

A
  • Yellow fever
  • St. Louis encephalitis
  • Dengue
  • Zika virus
79
Q

Zika virus is a member of the ________

A

Spondweni virus group

  • primarily through the bite of an infected Aedes mosquito
  • illness is mild (symptoms last days to a week)
  • fever, rash, joint pain, conjuctivitis, muscle pain, headaches
80
Q

Zika virus in Brazil

A

Reports of microcephaly and poor pregnancy outcomes in mothers who were infected with Zika virus while pregnant

Infectious Agents 2 (29 decks)

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